The impact of the third fragment features on the healing of femoral shaft fractures managed with intramedullary nailing: a radiological study

Femoral shaft fractures with third fragments have a high non-union rate, which may reach 14%. This study aims to assess the impact of the radiological features of the third fragment, evaluated on post-operative X-rays, on the outcome of femoral shaft fractures type 32-B managed with intramedullary nailing, in order to obtain an algorithm which could predict the fracture healing time.

We have retrospectively evaluated a series of 52 patients. On post-operative X-rays, four radiological parameters were evaluated: the third fragment angle, the fracture gap, the third fragment size, and the mean third fragment displacement. All the patients underwent a radiologic follow-up at one, two, three, six, nine and 12 months post-operatively, to assess the bone healing. The patients were then divided into three groups, according to the fracture healing time: within six months (group A), between six and 12 months (group B), or fracture non-union after 12 months (group C).

In 28 patients, out of 52 (53.85%), the fracture healing was observed at 6-month follow-up; in 18 patients, out of 52 (34.62%), the fracture healed within 12 months after trauma; and in six patients, out of 52 (11.54%), no fracture healing was observed at 12-month follow-up. The mean third fragment size was significantly different in each group (p < 0.05), while the mean third fragment displacement was significantly higher in group C, compared with group A (p = 0.0006) and group B (p = 0.0027). In group B, a positive correlation was found between the fracture healing time and the mean third fragment size (R = 0.594, p = 0.036); in group C, the fracture union time was positively related to the third fragment size (R = 0.689, p = 0.013) and the mean third fragment displacement (R = 0.7107, p = 0.006). Regression analysis showed that the third fragment size and the mean third fragment displacement are the most important features which affect the fracture healing time.

The third fragment size (cutoff 40 mm) is the leading parameter to influence the fracture healing within or in more than six months. The mean third fragment displacement (cutoff 12 mm); on the other hand, impacts on the fracture delayed rather than absent healing.